We look at the division of 350535 by 81 
The aim is to understand the frequency of 81 in 350535.

On to step 1:
81 can be fit into 3 0 times, resulting in a remainder of 3.
The next digit of our result is 0. 
Result so far: 0.0
If we subtract 0 from 3, we get 3.
Include the next digit (5) from the dividend after 3, then repeat: 35 / 81

Advancing to step 2:
The number 81 fits into 35 0 times, leaving a remainder of 35.
Record the quotient 0 as the next digit in the result. 
Result so far: 0.0
If we take 0 away from 35, we end up with 35.
Append the next digit (0) from the dividend to 35 and continue with: 350 / 81

On to step 3:
When dividing 350 by 81, we get 4 with a remainder of 26.
Put 4 as the next digit of the answer. 
Result so far: 4.0
Subtract 324 from 350 to get 26.
Fetch the next digit (5) from the dividend, attach it to 26 and continue: 265 / 81

Moving on to step 4:
81 goes into 265 3 times with a remainder of 22.
Use 3 as the next digit of our solution. 
Result so far: 43.0
Deduct 243 from 265 and we're left with 22.
Append the next digit (3) from the dividend to 22 and continue with: 223 / 81

Let's proceed to step 5:
If we divide 223 by 81, we get 2 and a remainder of 61.
The number 2 becomes the next digit in our result. 
Result so far: 432.0
The remainder is 61 after subtracting 162 from 223.
Take the next digit (5) from the dividend and append it to 61, then repeat: 615 / 81

Advancing to step 6:
If we divide 615 by 81, we get 7 and a remainder of 48.
The next digit of our result is 7. 
Result so far: 4327.0
If we take 567 away from 615, we end up with 48.
Since there are no more digits in the dividend, we add a zero to the remainder making it 480, and continue the process.

Moving on to step 7:
81 can be fit into 480 5 times, resulting in a remainder of 75.
Put 5 as the next digit of the answer. 
Result so far: 4327.5
If we subtract 405 from 480, we get 75.
Since there are no more digits in the dividend, we add a zero to the remainder making it 750, and continue the process.

On to step 8:
750 divided by 81 is 9 with a remainder of 21.
The next digit of our result is 9. 
Result so far: 4327.59
Subtract 729 from 750 to get 21.
Since there are no more digits in the dividend, we add a zero to the remainder making it 210, and continue the process.

Step 9:
81 can be fit into 210 2 times, resulting in a remainder of 48.
Use 2 as the next digit of our solution. 
Result so far: 4327.592
The remainder is 48 after subtracting 162 from 210.
Since there are no more digits in the dividend, we add a zero to the remainder making it 480, and continue the process.

Going ahead to step 10:
480 divided by 81 is 5 with a remainder of 75.
The next digit of our result is 5. 
Result so far: 4327.5925
If we take 405 away from 480, we end up with 75.
Since there are no more digits in the dividend, we add a zero to the remainder making it 750, and continue the process.

On to step 11:
If we divide 750 by 81, we get 9 and a remainder of 21.
The next digit of our result is 9. 
Result so far: 4327.59259
The remainder is 21 after subtracting 729 from 750.
Since there are no more digits in the dividend, we add a zero to the remainder making it 210, and continue the process.

Let's proceed to step 12:
81 can be fit into 210 2 times, resulting in a remainder of 48.
The number 2 becomes the next digit in our result. 
Result so far: 4327.592592
Subtracting 162 from 210 leaves us with 48.
Since there are no more digits in the dividend, we add a zero to the remainder making it 480, and continue the process.

Moving on to step 13:
When dividing 480 by 81, we get 5 with a remainder of 75.
The next digit of our result is 5. 
Result so far: 4327.5925925
If we subtract 405 from 480, we get 75.
Since there are no more digits in the dividend, we add a zero to the remainder making it 750, and continue the process.

Moving on to step 14:
81 goes into 750 9 times with a remainder of 21.
Put 9 as the next digit of the answer. 
Result so far: 4327.59259259
The remainder is 21 after subtracting 729 from 750.
Since there are no more digits in the dividend, we add a zero to the remainder making it 210, and continue the process.

Our division results in 4327.59259259 with a remaining 2.1e-08.